Serological responses of cats to feline immunodeficiency virus.
Hosie MJ; Jarrett O
Department of Veterinary Pathology, University of Glasgow, UK.
AIDS, 1990 Mar, 4:3, 215-20
The proteins of feline immunodeficiency virus (FIV) were identified
by sodium dodecylsulphate poly-acrylamide gel electrophoresis
(SDS-PAGE) and immunoblotting. Purified [35S]methionine/cysteine-
labelled virus contained proteins of Mr 120, 24, 17, and 10kD, of which
the most prominent were p24 and p17, and minor components of 62, 54,
52, 41 and 32kD. Sera from FIV-infected cats precipitated two
glycoproteins (gp) of Mr 120kD (gp120) and 41kD (gp41) from lysates
of [14C]glucosamine-labelled infected cells. Purified virus contained
very
little or no detectable glycoproteins. The serological response to
individual
viral proteins was followed in experimentally infected cats by
immunoblotting.
Since purified virus was a poor source of gp120, a method using
FIV-infected
cell lysates was developed. Cats produced antibodies to gp120, p55, p24
and
p17. (The p55 was presumed to be a precursor of p24 and p17.) Following
infection, antibodies developed first to p24 and subsequently to p17,
p55 and
gp120. Sera from cats infected with three separate isolates of FIV, two
from
the UK and one from the USA, had cross-reacting antibodies to all of
these
viral proteins. The criteria for identification of seropositive cats
were
defined.
The minimum requirement for a positive immunoblot was antibody to gp120
or to at least three core proteins (p55, p24 and p17). Comparison of two
commercial enzyme-linked immunosorbent assay (ELISA) kits and
immunoblotting indicated that false-positive results occurred as a
result of non-specific reactions in the ELISA systems.